1. Field of the Invention
The present invention relates to a keypad assembly, and in particular, to a keypad assembly in which an auxiliary layer having lower refractive index than that of a waveguide, for guiding a light, is formed on the surface of the waveguide.
2. Description of the Related Art
A “portable communication apparatus” refers to an electronic apparatus that is carried by a user and that is capable of performing wireless communication. Examples of the portable communication apparatus include HHPs (hand held phones), CT-2 cellular phones, digital phones, PCS (personal communication service) phones, and PDAs (personal digital assistants). Generally, portable communication apparatuses or portable wireless terminals are classified according to their appearance. For example, wireless terminals are classified into bar-type wireless terminals, flip-type wireless terminals, and folder-type wireless terminals. Such portable terminals are equipped with antenna, data input/output components, and data transmission/reception components. Keypads allowing data input through a finger press task are generally used as the data input/output components.
A keypad used for data input includes a plate-shaped elastic pad; a plurality of key buttons having characters printed thereon and being placed on the top surface of the elastic pad; and a plurality of protrusions on the bottom surface of the elastic pad. The portable terminals generally include a plurality of light emitting devices, typically 15-20 devices, for backlighting the key pad. The light emitting devices are of a top view type.
FIG. 1 is a cross-sectional view of a conventional keypad assembly 1. The keypad assembly 1 includes a keypad 2, a switch board 3, and a plurality of Light Emitting Diodes (LEDs) 4.
The keypad 2 includes an elastic pad 2a that is made of a flexible material (e.g., rubber) and that is plate-shaped; a plurality of key buttons 2b that are formed on the top surface of the elastic pad 2a and that has numbers and characters printed thereon; and a plurality of pressing protrusions 2c that are formed on the bottom surface of the elastic pad 2a. 
Each of the pressing protrusions 2c is arranged at the center of each of the key buttons 2b and a plurality of grooves 5 may be formed on the bottom surface of the elastic pad 2a. The grooves 5 are arranged around the pressing protrusions 2c in such a way to avoid interference caused by the LEDs 4 and the pressing protrusions 2c. 
The switch board 3 includes a plate-shaped Printed Circuit Board (PCB) and a plurality of dome switches 3a formed on the top surface of the PCB, facing the keypad 2.
The LEDs 4 are mounted on the top surface of the PCB and are positioned such that they are covered by the grooves 5 of the elastic pad 2a. 
If a user presses one of the key buttons 2b, a portion of the keypad 2 under the pressed key button 2b is deflected towards the switch board 3, and the pressing protrusion 2c under the deflected portion of the keypad 2 presses the dome switch 3a. A contact member 6 included in the dome switch 3a electrically contacts the pressing protrusion 2c. 
In the operations of the dome switches 3a, the LEDs 4 cannot be positioned under the key buttons 2b. As such, only a portion of light output from the LEDs 4 is used for illumination. Consequently, the conventional keypad 2 requires a large number of LEDs to illuminate the entire keypad 2 and large amount of power.
Moreover, the manufacturing process, the time required to manufacture the terminal, and the manufacturing cost of the terminal is exorbitant due to large number of parts required in the conventional terminal.